[Using game_loop with dartemis](http://dwayneb.free.fr/posts/using_gameloop_with_dartemis/)

dartemis_game_loop.dart

class Game {

  var _world;
  var _renderSystem;
  var _gameLoop; 

  Game(){
    // create instance
    var container = query("#game");
    _world = new World();
    _gameLoop = new GameLoopHtml(container);
    _renderSystem = new System_RenderX(container);

    // setup instance an allow circular dependencies gameLoop <-> world'system
    _setupWorld();
    _setupGameLoop();
  }

  void _setupWorld() {
    //...
    _world.addSystem(new System_XXXX());
    _world.addSystem(new System_YYYY(_gameLoop));
    // System(s) in charge of rendering will not run when world.process()
    _world.addSystem(_renderSystem, passive: true);
    _world.initialize();
  }

  void _setupGameLoop(){
    _gameLoop.pointerLock.lockOnClick = false; // to keep mouse cursor
    _gameLoop.onUpdate = (gameLoop){
      _world.delta = gameLoop.dt * 1000.0; // world.delta in ms
      _world.process();
    };
    _gameLoop.onRender = (gameLoop){
      _renderSystem.process();
    };
  }

  void start() => _gameLoop.start();
  void stop() => _gameLoop.stop();
}